Effect of heat treatment process on mechanical properties of super pipe nozzle for nuclear power plant

doi:10.13251/j.issn.0254-6051.2023.11.024

Abstract

Abstract: Effect and mechanism of performance heat treatment (PHT) and simulated welding heat treatment (SWHT) on mechanical properties were investigated for the P280GH steel super pipe nozzles produced by top-drawing process. Effects of different heat treatments on the microstructure were studied by means of optical microscope, scanning electron microscope and energy dispersive spectroscope, and the mechanical tests such as tensile tests at room temperature and 300 ℃, impact test at 0 ℃, Brinell hardness test were carried out. The results show that after PHT or PHT+SWHT, the microstructure of the nozzles are mainly composed of two phases of ferrite and pearlite. However, after PHT, the pearlite appears mainly at the grain boundary of ferrite, while after PHT+SWHT, the pearlite has a tendency of spheroidization, and there is some pearlite inside the ferrite. The tensile properties of the PHT nozzle specimens are basically the same as that un-heat-treated main pipe, but its average impact absorbed energy is higher by about 15 J. The tensile properties of the PHT+SWHT nozzle specimens are reduced by about 18 MPa compared to that un-heat-treated main pipe, and the average impact absorbed energy is reduced by about 20 J. It is shown that fracture and spheroidization of the pearlite in the microstructure of the super pipe nozzle produced by top-drawing are the main causes of changes in the mechanical properties of the specimens with different heat treatments.

Key words: nuclear power, super pipe, P280GH steel, performance heat treatment, simulated welding heat treatment

CLC Number:

TG162

Guo Yanhui, Deng Dong, Zhang Yue, Shen Yingcai, Wang Yan. Effect of heat treatment process on mechanical properties of super pipe nozzle for nuclear power plant[J]. Heat Treatment of Metals, 2023, 48(11): 156-160.

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